Instructions for engine operation Before putting an engine into operation and before each race are to be checked: - valve clearance adjustment - chain tension and tightening of screws on cam sprocket (in case of great chain clearance the valve timing is to be checked) - tension of primary and secondary chain - clutch adjustment - oil filling - working order of ignition cut-out - working order of carburettor (free motion of slide valve) Using of adequate thermal values of sparking plugs: - colder for long tracks Champion G 55 R - warmer for speedway Champion G 57 R Before using the engine at full throttle, the warming up of the engine is necessary. The choke may be used only for a very short time. Starting is accomplished by pushing or rear wheel rotating. At cold engine the choke is pulled out and starting without throttle follows. The starting is made easier by "winding-up" the engine first, i.e. slight turning of the rear wheel against the direction of turning until turning resistance appears. Then the usual starting follows.
Setting-up of ignition advance
The full engine power output depends on a suitable adjustment of advanced ignition. The advanced ignition of the engine occurs before the top dead center according to the table of technical data. The screw of checking hole on the L. H. crankcase will be loosed, the crankshaft moved round a slight amount to the advanced ignition mark in order to place it into the hole center. After releasing of screws turn slightly a stator in order to make the checking line of the stator aligned with that of rotor. Then tighten the screws of stator.
Lubrication of engine
The circulation-system lubrication is used. Oil is sucked through rough filter into pump and squeeze into crankshaft (connecting rod big-end bearing lubrication). The rough oil filter must be check after first running of new engine, and often clearing of this filter is recommended to avoid engine seizing. From crankshaft space is oil returned to oil tank through reed valve. Oil filling is recommended to be replaced after five or six heats.
Dismantling, assembly, adjustment and service life of engine Cylinder head and cylinder
Minimum thrust of valve springs when assembled has to be 300 N - this thrust ensure maximum engine speed 12000 rpm. The valve springs are checked as follows: after dismantling of rocker arms the valve is leant over suitable support against the plate of a balance and during the pressure of the head towards the balance, the values in kg are read just in the moment when the valve starts opening. This value may not drop below 30 kg (300N). If the value is lower the valve springs must be dismantled and check for free length, if the free length is not under 39 mm (valid for springs 889-13-163), then springs may be underlaid but the minimum clearance 1 mm between spring threads at the complete valve lift must be observed. - Width of intake seats 1,0-1,2 mm, round off the edges of valves and valve seats in the head. - Rocker arm roller must run freely without grabbing - Axial clearance of camshaft 0,2 - 0,4 mm - Replace the valve upper plates approximately after 30 races - Replace the camshaft drive chain approximately after 25 races -Combustion pressure is sealet by silicon ¨O¨ ring . -Please replace the O ring during every engine overhaul. -Compression ratio is adjusted by steel plates of different thickness under cylinder.
Repair works of crank mechanism are recommended to be made in specialized repair shops. The crank mechanism is pressed on cylindrical surfaces. Before pressing the interference size of pressed diameters has to be checked. The flywheels are forged together with main pin like one piece, the interference of crank pin at 0,11/0,13 mm. The crank mechanism can be pressed three times without using abnormal parts. The crank pin can be ordered in an abnormal modification with greater pin diameter for pressing by 0,025 mm. Axial clearance of crank mechanism in crankcase is 0,5-0,7 mm. Axial clearance of connecting rod in assembled crank mechanism should be 0,4-0,6 mm. The balancing of crank mechanism for horizontal engine has to be 52 % of balancing masses. - Clearance of gudgeon pin in piston must be 0,007-0,017 mm - Clearance in piston ring lock 0,30 - 0,35 mm - Please use the correct piston size for the cylinders bore according the table. For safety reasons replace the big end connecting rod bearing and piston after 15 races. During this the checking of connecting rod dimensions is recommended, the big end diameter should be 42,00/42,008mm (min/max), the radial clearance between crank pin and big end should be 0,037/0,052mm. The clearance between piston pin and small end should be for connecting rod 881-12-110: 0,02-0,04 mm (143 mm length)
Assembly of crank mechanism
Before assembly all parts must be cleaned. The crank pin must be oriented according the oil hole in right flywheel During pressing the holes (pins) should be slightly oiled to prevent pressed surfaces from seizing. After pressing balancing is necessary. Measurements are made in points and the run-out is measured 5 mm from flywheel faces and it should not exceed 0,03 mm. The highest value of run-out must be at the end of crank pin. The shaft of ignition rotor is carried separately in two bearings and is connected with the crankshaft by a clutch. When dismantling the ignition the proper throwing of the shaft in the small valve gear during the reassembly must be observed.
Valve gear mechanism
The camshaft is driven by chain directly from the crankshaft. The timing of valves is very easy; first by means of chain on cam sprocket and then final timing by means of oval holes on cam sprocket. The tightening of 4 screws on the sprocket must not be neglected. The values of cam timing are indicated in technical data.
These our instructions are recommended. In reality, take account of the riding style of the rider. In order to ensure the smooth service of our motorcycles we are prepared to train mechanics directly in JAWA Divišov a.s.
We wish all our customers full success with JAWA engines.
Výfuk a řetězy Exhaust and chains Auspuff und Kette